1. Field of the Invention
The present invention relates to a tester for semiconductor integrated circuits and a method for testing semiconductor integrated circuits, and more specifically to a tester for semiconductor integrated circuits comprising an A/D converter circuit to convert analog signals to digital signals, and a D/A converter circuit to convert digital signals to analog signals and a method for testing the semiconductor integrated circuits.
2. Background Art
The tester for semiconductor integrated circuit is called simply a tester. In recent years, in a system LSI constituted as a one-chip semiconductor integrated circuit constituted by a plurality of functionally systematized modules (1-chip LSI) or a hybrid integrated circuit in which chips of a plurality of circuits are combined (chip-set LSI), integration by combining high-performance, high-accuracy digital circuits and analog circuits (mixed-signalization) is being progressed rapidly, the testers for these semiconductor integrated circuits to cope with this mixed-signalization is also being progressed rapidly, and testers for testing mixed signal semiconductor integrated circuits are provided from tester manufacturers.
However, in order to accommodate the high-performance specifications of the mixed signal semiconductor integrated circuits, the testers tend to be expensive. Under such a situation, there has been a movement to avoid increase in the cost of tester through the reuse of existing low-speed, low-accuracy testers used, for example, for logic LSIs.
A significant problem to be solved in such testers is the test of D/A converter circuits to convert digital signals to analog signals and A/D converters to convert analog signals to digital signals. With increase in accuracy of these converter circuits, the problem is how to realize testers for semiconductor integrated circuits comprising these converter circuits at low cost.
In a general test circumstance for testers, along a measurement path from a measuring instrument inside the tester to the semiconductor integrated circuit to be tested (hereafter called DUT), there are a plurality of jigs to connect between the tester and the DUT, such as a DUT circuit board (DUT board) and cable, and the measurement path is long, causing noise to occur and measurement accuracy to be reduced, and it is difficult to test of plurality of the DUT at a time. Also, since a low-speed tester cannot test the DUT at a practical speed due to its speed restriction, increase in testing time for testing mass-produced DUTs is concerned.
Japanese Patent Laid-Open No. 1-316024 proposes a tester comprising a memory element for storing converted data in the address specified by input data to the D/A converter of the testing circuit, in which D/A converted analog signals are inputted to the A/D converter, the outputs of the A/D converter are sequentially stored in the memory element, the converted data stored in the memory element are sequentially transmitted to the tester when all the inputted data have been converted, and the inputted data are sequentially compared with the converted data in the tester.
However, since the inputted data to the D/A converter, the addresses of the memory element for storing converted data, and the control signals must be supplied from the tester, and furthermore, since the data stored in the memory element must be supplied to the tester, the measurement accuracy may be lowered due to noise in the long measurement path between the DUT and the tester. Also due to the occupation of the number of tester pin electronics, the simultaneous measurement of more than one DUT is difficult. Furthermore, since communication to transmit converted data to the tester takes much time, and the test results are judged after all the tests have been completed, the reduction of time is also difficult.
An object of the present invention is to solve such problems, and to provide a tester for semiconductor integrated circuits and a method for testing semiconductor integrated circuits that can realize high-speed, high-accuracy measurement at low costs.
Another object of the present invention is to realize high-speed, high accuracy measurement, and to provide a tester for semiconductor integrated circuits and a method for testing semiconductor integrated circuits that can test more than one semiconductor integrated circuits at a time.
According to one aspect of the present invention, a tester for semiconductor integrated circuits, comprises a testing circuit board configured to transmit signals to and receive signals from a semiconductor integrated circuit to be tested that comprises an A/D converter circuit to convert analog signals to digital signals and a D/A converter circuit to convert digital signals to analog signals, a test assisting device disposed in the vicinity of and connected to the testing circuit board; and a test machine connected to the test assisting device. The test assisting device comprises a data circuit to generate digital test signals and to supply the digital test signals to the D/A converter circuit of the semiconductor integrated circuit to be tested, a testing D/A converter circuit to convert the digital test signals from the data circuit to analog test signals and to supply the analog test signals to the A/D converter circuit of the semiconductor integrated circuit to be tested, a testing A/D converter circuit to convert analog test outputs from the D/A converter circuit of the semiconductor integrated circuit to be tested to digital test outputs, a measured data memory to store the digital test outputs from the A/D converter circuit of the semiconductor integrated circuit to be tested and the digital test outputs of the testing A/D converter circuit, and an analyzer portion to analyze each of the digital test outputs stored in the measured data memory. The tester for semiconductor integrated circuits is configured to supply the digital test signals and the analog test signals to the semiconductor integrated circuit to be tested based on instructions from the test machine, and to supply the results of analysis of each digital test output stored in the measured data memory by the analyzer portion to the test machine.
According to another aspect of the present invention, a method for testing semiconductor integrated circuits comprising an A/D converter circuit for converting analog signals into digital signals, and a D/A converter circuit for converting digital signals into analog signals, wherein the test of the semiconductor integrated circuit is conducted in such a manner. A test assisting device is disposed in the vicinity of a testing circuit board configured to transmit signals to and receive signals from the semiconductor integrated circuit to be tested. The test assisting device have a data circuit for generating digital test signals to supply the digital test signals to the D/A converter circuit of the semiconductor integrated circuit to be tested, a testing D/A converter circuit for converting the digital test signals from the data circuit into analog test signals to supply the analog test signals to the A/D converter circuit of the semiconductor integrated circuit to be tested, a testing A/D converter circuit for converting analog test outputs of the D/A converter circuit of the semiconductor integrated circuit to be tested into digital test outputs, a measured data memory for storing the digital test outputs from the A/D converter circuit of the semiconductor integrated circuit to be tested and the digital test outputs of the testing A/D converter circuit, and an analyzer portion to analyze each of the digital test outputs stored in the measured data memory. The digital test signals and the analog test signals are supplied to the semiconductor integrated circuit to be tested according to instructions from a test machine, and the results of analysis of respective digital test outputs stored in the measured data memory by the analyzer portion are supplied to the test machine.
According to the present invention, since the test assisting device disposed in the vicinity of the testing circuit board is provided with a data circuit, a testing D/A converter circuit, a testing A/D converter circuit, a measured data memory, and a DSP analyzing portion, and the test assisting device is made to conduct the test of the A/D converter circuit and the D/A converter circuit of a semiconductor integrated circuit to be tested, the test of a mixed signal type semiconductor integrated circuit comprising an A/D converter circuit and a D/A converter circuit can be conducted at high accuracy and high speed, and the cost reduction of the tester can be achieved.
Other and further objects, features and advantages of the invention will appear more fully from the following description.